Engine: F9Q

Winter is coming and I've noticed that when parked over night and outside temperatures are around 0C my engine takes longer than usual to start. Not that it's any problem, yet, but I'm thinking it might be a warning that there will be a problem starting when it gets colder.

Normally this car starts within 2 seconds holding the key in start position, even in winter. Now, at 0C outside, it takes more like 5 seconds to start. On days when outside temperature is more than 3C, it starts within 2 seconds, as normal.

I suspect the glowing system to be the cause of this. BUT, I've had a failing glow relay before, and that caused the glow indicator light to not show before starting. Now the glow indicator comes on as normal.

I've had a glow plug failure before as well. That did throw a fault code, with a red warning light in the dash. And even with a totally dead glow plug, the engine did start within the normal 2 seconds, even in -10C.

As a result of the mentioned events, I replaced all of the glow plugs and and the relay a few years ago.

As far as I know, there isn't really anything else to the glow system. What else could be causing this?

Battery is good - starter turns the engine in normal speed. Fuel filter issues should be showing other symptoms as well, which this car does not show.

This morning it was -1C outside. Then I measured the glowplugs. The resistance between glowplug + and a screw on the engine block was 0.53, 0.55, 0.67 and 0.69 ohms. While all plugs were disconnected I had 11.95V on the wires while glowing. Battery voltage was 12.43V while glowing. When switching ignition off, the voltage on the wires dropped to 10.65V, and it stayed there until one of the wires got connected to a glowplug. Then the voltage dropped to 0 quickly. All cables had the same voltage.

What I find strange is that 11.95V is quite a drop from 12.43V when there should be no current running in the circuit, other than the voltmeter. Does this indicate current leaking to ground in the glow circuit?

Outside temperature climbed from -10ish to +5C. With warm weather it starts without any hesitation. But it also started to throw fault code P0670 on every cold start. Letting the engine run for a few minutes, then restart, and the fault code is gone. If restarted too soon after a cold start, the fault is still there. So, obviously something is wrong with the glowing system. I just can't figure out what it is.

If the glow relay was screwed, it wouldn't have started at all in the cold. All glow plugs resistance is in the range 0,5-0,7ohms while installed. All plugs gets voltage around 12V while glowing. What could be causing this issue when all measurements seems ok?

I'm tempted to order new glow plugs just for the lack of alternatives.

If yours have been in a couple of years, it maybe worth renewing them.

Thanks for the tip on testing the plugs.

They are from 2016. This car has only been driving 35,000km with them. I'm disapointed by their lifetime. My other P12 has been driven 140,000km over 11years without any glow plug issues.

I just realized that my parts supplier had new plugs for €2.5 + shipping, so I ordered 8 plugs with combined shipping. Wonder if they'll send it, as the price should probably have been €12.5.

Keep the old 3 as your spares.

Still hard to start in cold. I'll replace the reminding plugs.

Actually I see it as a negative thing if they all wear down the same. That mean when you run into trouble, you'll end up not being able to start the car while waiting for new parts.